13,809 research outputs found
Impact of FCNC top quark interactions on BR(t -> b W)
We study the effect that FCNC interactions of the top quark will have on the
branching ratio of charged decays of the top quark. We have performed an
integrated analysis using Tevatron and B-factories data and with just the
further assumption that the CKM matrix is unitary we can obtain very
restrictive bounds on the strong and electroweak FCNC branching ratios Br(t ->
q X) < 4.0 10^{-4}, where X is any vector boson and a sum in q = u,c is
implied.Comment: 10 pages, 5 figure
Contributions from dimension six strong flavor changing operators to top anti-top, top plus gauge boson, and top plus Higgs boson production at the LHC
We study the effects of a set of dimension six flavor changing effective
operators on several processes of production of top quarks at the LHC. Namely,
top anti-top production and associated production of a top and a gauge or Higgs
boson. Analytical expressions for the cross sections of these processes are
derived and presented.Comment: 14 pages, 10 figures, refs. adde
Charge and CP symmetry breaking in two Higgs doublet models
We show that, for the most generic model with two Higgs doublets possessing a
minimum that preserves the symmetry, charge breaking (CB) cannot
occur. If CB does not occur, the potential could have two different minima, and
there is in principle no general argument to show which one is the deepest. The
depth of the potential at a stationary point that breaks CB or CP, relative to
the preserving minimum, is proportional to the squared mass of the
charged or pseudoscalar Higgs, respectively
Flavour changing strong interaction effects on top quark physics at the LHC
We perform a model independent analysis of the flavour changing strong
interaction vertices relevant to the LHC. In particular, the contribution of
dimension six operators to single top production in various production
processes is discussed, together with possible hints for identifying signals
and setting bounds on physics beyond the standard model.Comment: Authors corrections (references added
Strong flavour changing effective operator contributions to single top quark production
We study the effects of dimension six effective operators on the production
of single top quarks at the LHC. The operator set considered includes terms
with effective gluon interactions and four-fermion terms. Analytic expressions
for the several partonic cross sections of single top production will be
presented, as well as the results of their integration on the parton density
functions.Comment: 20 pages, 7 fig
Effects of a CPT-even and Lorentz-violating nonminimal coupling on the electron-positron scattering
We propose a new \emph{CPT}-even and Lorentz-violating nonminimal coupling
between fermions and Abelian gauge fields involving the CPT-even tensor
of the standard model extension. We thus
investigate its effects on the cross section of the electron-positron
scattering by analyzing the process .
Such a study was performed for the parity-odd and parity-even nonbirefringent
components of the Lorentz-violating tensor.
Finally, by using experimental data available in the literature, we have
imposed upper bounds as tight as on the magnitude of the
CPT-even and Lorentz-violating parameters while nonminimally coupled.Comment: LaTeX2e, 06 pages, 01 figure
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